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/*
* FILE: transcoder.c
* PROGRAM: Rat
* AUTHOR: Colin Perkins
*
* Based on auddev_mux.c, revision 1.11
*
* Copyright (C) 1996-2001 University College London
* All rights reserved.
*/
#ifndef HIDE_SOURCE_STRINGS
static const char cvsid[] =
"$Id: transcoder.c,v 1.13 2001/01/08 20:30:11 ucaccsp Exp $";
#endif /* HIDE_SOURCE_STRINGS */
#include "config_unix.h"
#include "config_win32.h"
#include "memory.h"
#include "audio_types.h"
#include "transcoder.h"
#define CHANNEL_SIZE 8192
#define NUM_CHANNELS 2
static int num_open_channels = 0;
static sample *channel[NUM_CHANNELS+1];
static int head[NUM_CHANNELS+1];
static int tail[NUM_CHANNELS+1];
static struct timeval last_time[NUM_CHANNELS+1];
static struct timeval curr_time[NUM_CHANNELS+1];
static int first_time[NUM_CHANNELS+1];
int
transcoder_open(void)
{
/* Open a fake audio channel. The value we return is used to identify the */
/* channel for the other routines in this module. The #ifdefs in net.c */
/* prevent it being used in a select(). */
/* Note: We must open EXACTLY two channels, before the other routines in */
/* this module function correctly. */
int id, i;
assert((num_open_channels >= 0) && (num_open_channels < NUM_CHANNELS));
id = ++num_open_channels;
head[id] = 0;
tail[id] = 0;
first_time[id] = 0;
channel[id] = (sample *) xmalloc(CHANNEL_SIZE * sizeof(sample));
for (i=0; i<CHANNEL_SIZE; i++) {
channel[id][i] = L16_AUDIO_ZERO;
}
return id;
}
void
transcoder_close(int id)
{
assert(num_open_channels > 0);
assert(id > 0 && id <= num_open_channels);
xfree(channel[id]);
num_open_channels--;
}
int
transcoder_read(int id, sample *buf, int buf_size)
{
int i, read_size, copy_size;
assert(buf != 0);
assert(buf_size > 0);
assert(id > 0 && id <= num_open_channels);
assert(head[id] <= CHANNEL_SIZE);
assert(tail[id] <= CHANNEL_SIZE);
assert(head[id] <= tail[id]);
if (first_time[id] == 0) {
gettimeofday(&last_time[id], NULL);
first_time[id] = 1;
}
gettimeofday(&curr_time[id], NULL);
read_size = (((curr_time[id].tv_sec - last_time[id].tv_sec) * 1000000) + (curr_time[id].tv_usec - last_time[id].tv_usec)) / 125;
if (read_size > buf_size) read_size = buf_size;
for (i=0; i<read_size; i++) {
buf[i] = L16_AUDIO_ZERO;
}
last_time[id] = curr_time[id];
copy_size = tail[id] - head[id]; /* The amount of data available in this module... */
if (copy_size >= read_size) {
copy_size = read_size;
} else {
#ifdef DEBUG_TRANSCODER
printf("transcoder_read: underflow, silence substituted -- want %d got %d channel %d\n", read_size, copy_size, id);
#endif
}
assert((head[id] + copy_size) <= tail[id]);
for (i=0; i<copy_size; i++) {
buf[i] = channel[id][head[id] + i];
}
head[id] += copy_size;
assert(head[id] <= CHANNEL_SIZE);
assert(tail[id] <= CHANNEL_SIZE);
assert(head[id] <= tail[id]);
return read_size;
}
int
transcoder_write(int id, sample *buf, int buf_size)
{
int i;
assert(buf != 0);
assert(buf_size > 0);
assert(id > 0 && id <= num_open_channels);
assert(head[id] <= CHANNEL_SIZE);
assert(tail[id] <= CHANNEL_SIZE);
assert(head[id] <= tail[id]);
if ((tail[id] + buf_size) > CHANNEL_SIZE) {
for (i=0; i < (CHANNEL_SIZE - head[id]); i++) {
channel[id][i] = channel[id][i + head[id]];
}
tail[id] -= head[id];
head[id] = 0;
}
assert((tail[id] + buf_size) <= CHANNEL_SIZE);
for (i=0; i<buf_size; i++) {
channel[id][tail[id] + i] = buf[i];
}
tail[id] += buf_size;
assert(head[id] <= CHANNEL_SIZE);
assert(tail[id] <= CHANNEL_SIZE);
assert(head[id] <= tail[id]);
return buf_size;
}
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